jdowning
Oud Junkie
Posts: 3485
Registered: 8-2-2006
Location: Ontario, Canada
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Water Based Shellac Varnish.
Forum member Edward Powell recently was curious about the possibility of preparing shellac varnish without use of organic solvents such as alcohol -
for those who have adverse reactions to the vapours of these chemicals.
The ability to dissolve shellac in water is well established but may not be generally well known. Shellac will dissolve in water (aqueous solution) if
added to alkali solutions - borax, sodium carbonate, ammonia being the most readily available alkalis. Borax in particular is often used for the
purpose as a safe chemical.
The aqueous shellac solution may then be employed as a varnish that is a lot slower drying (3X - by evaporation) than shellac in alcohol - so may have
additional advantages in applying the shellac 'streak free'?
I am mainly interested in aqueous shellac as a potential hardener or property modifier for wood (pressure impregnation) or binder for silk strings -
all yet to be tested.
However, as preparation of aqueous shellac as a varnish would appear to be straightforward, I thought that it might be of interest to post this 'how
to do it' information here.
http://www.workbenchdiary.com/2011/11/making-aqueous-shellac.html
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antekboodzik
Oud Junkie
Posts: 109
Registered: 5-24-2010
Location: north poland
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Very interesting.
However, may I post some issues?
- wouldn't such a mixture raise grain of wood?
- I wonder if it would penetrate wood less or more than alcohol based shellac,
- doing so wouldn't destroy e. g. top of the instrument moisturing it and/or braces, causing abnormal expansion and then shinkage?
- may it be possible to use water based tints and dyes to provide interesting variations of colours? It could be especially nice when using on
pre-covered wood,
- how about using a combination of shellac and other, less than 96,6% alcohol liquids  May it be a reciepe of shellac dissolved in 40% or 50% vodka (or even yet stronger moonshine) would have combine advantages of reasonably
quick drying finish, but still streak free and thus easier to get good results?
- maybe some other alcohol drinks produce interesting variations of colors to the finish? How about advertising it in such a way: "The finish based on
best whiskey" etc...
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jdowning
Oud Junkie
Posts: 3485
Registered: 8-2-2006
Location: Ontario, Canada
Member Is Offline
Mood: No Mood
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Grain raising is usually part of the finishing process prior to any varnishing so if the first coat of aqueous shellac does this then that would not
be a problem.
I don't know the relative penetration rates into wood of alcohol based shellac and aqueous shellac. Not much difference for wiped on surface finishes
I would imagine.
Best not to varnish the sound board of an oud but if you did apply aqueous shellac as a thin, wiped on finish I doubt if it would result in damage to
the wood of the sound board or create problems any more than the use of water based hide glues would - e.g. when gluing braces, bridge, shams,
bindings, inlays, pick guards etc. as well as the sound board to bowl.
I imagine that shellac will only dissolve in an aqueus solution of alcohol if it is made into an alkali solution by the addition of borax etc. - but I
have not tried it to find out.
Shellac can be de-waxed by dissolving in alcohol, allowing the solution to stand for some time and then decanting the clear wax free shellac solution.
This solution might then be concentrated by evaporation and blended with alkaline water to form aqueous shellac. I have not tried this approach but it
would probably work.
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